Combining St. John’s Wort With Prescription Drugs May Be Lethal

A new study from Wake Forest Baptist Medical Center reports that St. John’s wort, which is the leading complementary and alternative treatment for depression in the United States, is possibly dangerous when combined with common prescription drugs.

When taking the herbal supplement, patients can experience a reduced concentration of many drugs including, oral contraceptive, blood thinners, cancer chemotherapy and blood pressure medications. This can result in impaired effectiveness and treatment failure.

“Patients may have a false sense of safety with so-called ‘natural’ treatments like St. John’s wort,” said Sarah Taylor, MD, assistant professor of dermatology at Wake Forest Baptist and lead author of the study. “And it is crucial for physicians to know the dangers of ‘natural’ treatments and to communicate the risks to patients effectively.”

The team conducted a retrospective analysis of nationally representative data collected by the National Ambulatory Medical Care Survey to determine the amount of St. John’s wort prescribed or taken with other medication. In 28 percent of the cases reviewed, the team discovered potentially harmful drug combinations.

Potential harmful interactions include the possibly fatal serotonin syndrome, which causes high amount of serotonin to accumulate in the body, heart disease from impaired function of blood pressure medications and unplanned pregnancy from contraceptive failure.

This study was limited because only the medications recorded by a physician were analyzed. Since the database analyzed did not include patients who did not report their use of St. John’s wort, the rate of interactions is likely underestimated.

“Labeling requirements for helpful supplements such as St. John’s wort need to provide appropriate cautions and risk information,” Taylor said, adding that France has banned the use of St. John’s wort products and several other countries, including Japan, the United Kingdom, and Canada, are in the process of including drug-herb interaction warnings on St. John’s wort products.

“Doctors also need to be trained to always ask if the patient is taking any supplements, vitamins, minerals or herbs, especially before prescribing any of the common drugs that might interact with St. John’s wort.”